There are many techniques for viewing stereoscopic images. Techniques using polarized glasses, LCD glasses, lenticular screens, interleaved screens and two separate screens employ specialized processes that require additional hardware and expense. Anaglyphic methods using red/green glasses are inexpensive and simple to implement, but the filters distort the color images and can be difficult to use for extended periods of time.
Split images (adjacent side-by-side images on a screen) provide faithful color and image reproduction. Devices using side-by-side left and right images date back to the late 1800's. There are many patents on stereoscopic viewers using standard interpupillary distances, with left and right images viewed at short focal lengths in a hand held fixture. Other patents describe hand held viewers or glasses for viewing left and right stereoscopic images from greater distances. Some patents describing viewers or glasses include U.S. Pat. No. 1,520,311 (Ruth), U.S. Pat. No. 2,849,917 (Petri), U.S. Pat. No. 4,730,898 (Curtin), and U.S. Pat. No. 4,986,632 (Eckmann). The devices usually contain lenses or lens prisms, and some form of light block to separate the left and right images.
Left and right images formed on a single screen may also be viewed with glasses that contain mirrors that increase the center distance between left and right screen images. An extension to this concept is presented in U.S. Pat. No. 5,357,369 (Pilling et al) where mirrors are placed in a hood mounted on the display and rotate the image 90 degrees to fill the entire screen with the left and right images. U.S. Pat. No. 5,126,878 (Trumbull et al) presents another split screen approach which uses horizontal compression techniques and employs special glasses that expand the viewed image back to correct proportions.
There is a need for a stereoscopic viewing system that uses a standard display and, which can be viewed with glasses or a visor employing inexpensive and non-critical components. The system should achieve the largest viewing screen area possible for increased image resolution, while maintaining correct color and image proportions. Ideally, the system should also reduce image processing requirements by minimizing the image area containing overlapping visual information.